skill-creator

A tool for creating a new skill for a coding agent when someone explicitly asks for a new capability. It adds the required metadata, checks the result, and saves it.

In plain words
What is it for?
Use it to scaffold and validate a new skill in response to a request such as “add a skill for X.”
Why use it?
It removes the need to remember the file format and setup rules for agent skills. It also keeps skill creation tied to a clear human request.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/yologdev/yoyo-evolve/skill-creator
Any agent
npx skills add yologdev/yoyo-evolve --skill skill-creator
Clone the repo
git clone --depth 1 https://github.com/yologdev/yoyo-evolve

Made for: Claude Code, Codex.

Per session 46 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,203 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00046 $0.03203
Opus 5 $0.00023 $0.01602
Sonnet 5 $0.00009 $0.00641
Haiku 4.5 $0.00005 $0.00320

Measured yesterday against content hash b9de48c43e6f, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

skill-creator scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured yesterday.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

- The skill content MUST be downloaded in this same session from a verifiable URL (curl/git/gh). Record the URL in the skill's body under a `## Source` section.
skills/skill-creator/SKILL.md · 255 lines

How it starts

The opening of the file, as written. The whole thing — 255 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Skill Creator

You are creating a new yoyo skill on demand, in direct response to an explicit request — either from the human creator or from a community issue asking for a new capability.

skill-creator vs skill-evolve

These are complementary, not redundant. Use the right one:

Question skill-creator (this skill) skill-evolve
Who triggers it? Human creator OR community issue (explicit ask) GitHub Actions cron (autonomous)
When does it run? Inside a normal evolve session, on demand Hourly cron at :30, gated by 5-session counter + 24h cooldown
What signals does it use? The user's request Past-session evidence (learnings, journal, audit-log)
Recurrence gate? No (human is in the loop) Yes (≥3 sessions for create)
Diff-scope guard? None — runs in evolve session Yes — scripts/skill_evolve.sh enforces
Auto-commit? Yes (inside evolve session's commit flow) Yes (after diff-scope + build/test gates)

Rule of thumb: if no human asked, you're not creating a skill — you're noticing a pattern. Write it to memory/learnings.jsonl with a pattern_key and let skill-evolve pick it up on the next cycle.

When NOT to use this skill

  • You're inside a scripts/skill_evolve.sh cycle. Use the Create branch in skills/skill-evolve/SKILL.md instead — it has the right gates (recurrence, dedup, ≤25 cap).
  • You noticed a recurring pattern but no one asked. Write a learning with pattern_key; skill-evolve owns autonomous creation.
  • The user asked for a one-off helper that won't be invoked again. Just write it inline; don't litter skills/.

When to use this skill

  • The human creator (Yuanhao) tells you "scaffold a new skill for X"
  • A community issue says "please add a skill for X" and you decide during a normal evolve session that the request is concrete enough to act on
  • You're installing a third-party skill from outside the repo (uses origin: marketplace or origin: gh:author/repo)

Procedure

Read the full file on GitHub · 255 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. yesterday First seen · 255 lines · 46 tokens per session scan A b9de48c43e6f

Subscribe to this mod's changes

skill-creator is a skill published in the GitHub repository yologdev/yoyo-evolve (1,868 stars, last pushed yesterday), licensed MIT. It adds 46 tokens to every session and 3,203 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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